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https://github.com/carbon-language/carbon-lang.git
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Richard Smith
dd7cfdb149
Implement the alias rules from proposal #5389, wherein an alias is permitted so long as the target has a constant value. While that proposal is not yet accepted, this seems like a reasonable basis for further iteration, and will be useful for the examples we're currently pursuing.
68 lines
2.4 KiB
C++
68 lines
2.4 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "toolchain/check/context.h"
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#include "toolchain/check/generic.h"
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#include "toolchain/check/handle.h"
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#include "toolchain/check/inst.h"
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#include "toolchain/check/modifiers.h"
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#include "toolchain/check/name_component.h"
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#include "toolchain/parse/node_ids.h"
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#include "toolchain/sem_ir/ids.h"
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#include "toolchain/sem_ir/typed_insts.h"
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namespace Carbon::Check {
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auto HandleParseNode(Context& context, Parse::AliasIntroducerId /*node_id*/)
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-> bool {
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// Aliases can't be generic, but we might have parsed a generic parameter in
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// their name, so enter a generic scope just in case.
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StartGenericDecl(context);
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// Optional modifiers and the name follow.
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context.decl_introducer_state_stack().Push<Lex::TokenKind::Alias>();
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context.decl_name_stack().PushScopeAndStartName();
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return true;
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}
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auto HandleParseNode(Context& /*context*/,
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Parse::AliasInitializerId /*node_id*/) -> bool {
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return true;
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}
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auto HandleParseNode(Context& context, Parse::AliasId /*node_id*/) -> bool {
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auto [expr_node, expr_id] = context.node_stack().PopExprWithNodeId();
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auto name_context = context.decl_name_stack().FinishName(
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PopNameComponentWithoutParams(context, Lex::TokenKind::Alias));
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DiscardGenericDecl(context);
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auto introducer =
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context.decl_introducer_state_stack().Pop<Lex::TokenKind::Alias>();
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LimitModifiersOnDecl(context, introducer, KeywordModifierSet::Access);
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auto entity_name_id = context.entity_names().Add(
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{.name_id = name_context.name_id_for_new_inst(),
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.parent_scope_id = name_context.parent_scope_id});
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if (!context.constant_values().Get(expr_id).is_constant()) {
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CARBON_DIAGNOSTIC(AliasRequiresConstantValue, Error,
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"alias refers to a runtime value");
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context.emitter().Emit(expr_node, AliasRequiresConstantValue);
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}
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auto alias_id = AddInst<SemIR::AliasBinding>(
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context, name_context.loc_id,
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{.type_id = context.insts().Get(expr_id).type_id(),
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.entity_name_id = entity_name_id,
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.value_id = expr_id});
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// Add the name of the binding to the current scope.
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context.decl_name_stack().PopScope();
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context.decl_name_stack().AddNameOrDiagnose(
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name_context, alias_id, introducer.modifier_set.GetAccessKind());
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return true;
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}
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} // namespace Carbon::Check
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